If you want to build one with foam core, it will have more twist and wobble than a solid core.It may work for low wind cruising. At 15mph or above it will wobble and shake. If you do high speed racing or jumping, Solid Core Carbon Fiber is the way to go.

If you want to build one with foam core, it will have more twist and wobble than a solid core....

You Can stabilize the foam-core, (cradle) with ply on the flat side and 3oz glass on the airfoilside ; then use it as you would use a female mold. ORStabilize the airfoil itself with 3oz glass , then make a female mold of That , to dothe lay-up in.

PFP molds are the easiest for testing, but a conventional mold of glass & epoxy , withan epoxy surface-coat, is the best way to learn mold-making.

You can get Reasonable accuracy with Both these methods.

Seriously, if i was a Despicable Low-life, it would be EASY to mold a (state of the art) hydrofoil, then build a copy from the mold. I got a cold Beer that says the ONLYperson here that could tell My copy from the real thing, would be the manufacturerhimself. The resolution would be a dead give-away, but i would spray the moldwith a clear-coat First, then do the lay-up and come back and shine the finish tonear perfection.

The point is :"Ya do NOT need a $20,000 mold, to make Good parts out of" !!

On my high AR wood front fin the span was 25 inches long, it was flexing too much, so I fiberglassed it and sand and fiberglass and sand and it still flexes. Fiberglass does not seem to work in high stress environment in hydrofoils. My titanium high AR front wing was showing better speed than the factory carbon wings. My GPS clocked 15 knot top speed with 7 knot winds while the factory wing only did 13 knots. A 1/3 frontal area really helps.

Water is hundred times more dense than air, the stress a hydrofoil faces is much more than hangliders

I realize that water as a Bunch denser, and it's why i asked how you wrapped your wood core foil ?

The stress goes through your foil, the same way it goes through a gliderwing, (just More of it in water) . If you wrapped it + - 90deg to the span-wise , you did essentially Nothing to take care of the twisting moment. You Did say itstill bends !!

The forum is suppose to be a learning tool ; hope your Not getting pissed because i'm gathering as Much info as i can here.

I lay the fiberglass 90 degrees. The vibration creates a loud low frequency noise. Any vibration will create more drag than a rigid wing. In the French forum, they are talking about using prepreg high modulus carbon fiber to make the foil more rigid.

I lay the fiberglass 90 degrees. The vibration creates a loud low frequency noise. Any vibration will create more drag than a rigid wing. In the French forum, they are talking about using prepreg high modulus carbon fiber to make the foil more rigid.

Got a cold Beer, that says i Know where that resident-frequency is coming from ;stress & the lack of addressing it.

Did you know that Ya can make that Pre-preg stuff, ((Yourself)) ?but even with the use of (Pre-Preg) ; unless the fibers are going inthe correct direction, Ya -- (("Still" got nothing )) !!

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